There are many situations in which the angle between two surfaces needs to be measured. For instance, carpenters frequently need to measure angles between walls to determine whether the required specifications have been met. There are many different devices which can be used to measure the inner angle between two planar surfaces. Generally such devices consist of two pivotally joined arms which are joined by a protractor arc indicating the angle between the two arms. Various configurations applying this general principle are known in the art.
However, there are instances when the measure of the inner angle between two surfaces is either irrelevant, inaccessible, or less convenient. In situations where the outer angle is important, the above-mentioned devices have failed to provide a convenient and accurate tool. The prior art devices which are capable of measuring inner angles generally cannot be extended beyond 180 degrees because of the limited span of the measuring arc used. Therefore, two separate instruments have been required to measure both inner and outer angles.
Therefore, while devices capable of measuring inner angles are well known, there is a need for a single device which is capable of conveniently measuring both the inner and outer angles between two surfaces.